Fix pandas 1.5+ FutureWarning in .str.split(..., expand=True)

[JacobHayes]

• Closes .str.split(..., expand=True) with Int64Index triggers pandas FutureWarning #9703
• Tests added / passed
• Passes pre-commit run --all-files

I confirmed manually that this removed the warning with the repro code in #9703, but didn't add an explicit test for it.

[GPUtester]

Can one of the admins verify this patch?

Admins can comment ok to test to allow this one PR to run or add to allowlist to allow all future PRs from the same author to run.

[ncclementi]

add to allowlist

[phobson]

@JacobHayes this looks good and fixes the issue on my system. Do you mind if I push a commit that adds a test to the PR?

[JacobHayes]

@phobson

@JacobHayes this looks good and fixes the issue on my system. Do you mind if I push a commit that adds a test to the PR?

That'd be great, thanks!

[phobson]

@JacobHayes turns out I don't have the credentials to do that.

Right here, can you add:

@pytest.mark.parametrize("index", [None, [0]], ids=["range_index", "other index"])
def test_str_split_no_warning(index):
    df = pd.DataFrame({"a": ["a\nb"]}, index=index)
    ddf = dd.from_pandas(df, npartitions=1)

    pd_a = df["a"].str.split("\n", n=1, expand=True)
    dd_a = ddf["a"].str.split("\n", n=1, expand=True)

    assert_eq(dd_a, pd_a)

[JacobHayes]

Ah, great - I should have expected filterwarnings=error:::pandas[.*] in the pytest setup! Added the test, thanks for walking me through it. :)

[jrbourbeau]

Thanks @JacobHayes, this looks great!

Note the test failure here is unrelated to the changes in this PR and being handled over in #9701

Also, I noticed this is your first code contribution to this repository. Welcome!